JPWO2016075871A1 - Control method of arc welding - Google Patents

Abstract

In the control of consumable electrode arc welding, in which pulse welding and short-circuit welding are alternately repeated, the forward and reverse feeds of the welding electrode are periodically repeated during the short-circuit welding period (Ts), and the welding current ends at the end of the pulse period. By starting normal feeding of the welding electrode at a time smaller than the immediately preceding base current, it is possible to suppress spatter generation and realize stable welding.

Description

  The present invention relates to a consumable electrode type arc welding control method in which a pulse welding period and a short-circuit welding period are alternately repeated.

  Representative examples of the consumable electrode type arc welding method include pulse welding and short-circuit welding, which are put to practical use. However, pulse welding and short circuit welding have the following problems.

  Pulse welding has a low heat input compared to spray transfer with a constant current exceeding the critical current, but since a long arc length is required to maintain a stable pulse transfer, the heat input cannot be kept low. Therefore, in so-called posture welding such as upright or upward, a bead having a defective shape such as bead drooping tends to occur.

  In short-circuit welding, the arc length is short and the heat input by the arc is small during the short-circuit period, so that welding defects such as poor fusion are likely to occur. In addition, there are many spatters due to short arc length and short circuit.

  As means for suppressing the above problems, there has been proposed an arc welding method in which pulse welding and short-circuit welding are controlled to be repeated alternately every arbitrary number of times (see Patent Document 1). FIG. 4 shows a welding current waveform in the conventional arc welding control disclosed in Patent Document 1. The welding current is controlled so that pulse welding and short-circuit welding are alternately performed for a set number of times. Further, the welding wire is fed at a constant feeding speed so as to be an optimum value in each of pulse welding and short-circuit welding. Thus, Patent Document 1 describes that heat input control and bead shape control can be performed to suppress generation of defective defects such as welding defects such as poor fusion and bead sag in posture welding.

  Moreover, in short-circuit welding, as a method for suppressing spatter generation and reliably performing short-circuit transition, arc generation and short-circuit detection are detected, and a welding wire is fed (normal feed) by the generation of the arc. A welding method in which the wire is pulled up (reversely fed) by generation is shown (see Patent Document 2).

JP-A-60-255276 Japanese Patent Publication No. 48-11463

  In the consumable electrode type arc welding in which the pulse welding period and the short-circuit welding period are alternately repeated, the forward feed and the reverse feed of the welding wire are repeated at a constant cycle during the short-circuit welding period. When moving from the pulse welding period to the short-circuit welding period, the welding wire starts to be fed in the forward feed direction when the current is smaller than the base current immediately before the end of the pulse welding period.

1A is a schematic configuration diagram of an arc welding apparatus according to Embodiment 1. FIG. FIG. 1B is a schematic enlarged cross-sectional view showing a welding part of arc welding in the first embodiment. FIG. 2 is a diagram showing a welding current, a welding voltage, and a welding wire feeding speed in arc welding in the first embodiment. FIG. 3 is a diagram showing a welding current, a welding voltage, and a welding wire feeding speed in arc welding in the second embodiment. FIG. 4 is a diagram showing a welding current in conventional arc welding.

(Embodiment 1)
FIG. 1A is a schematic configuration diagram of an arc welding apparatus 50 according to the first embodiment. The arc welding apparatus 50 mainly feeds a welding power source 19 that supplies power between a welding wire 15 that is a welding electrode that is a consumable electrode and a welding object 18, a welding torch 16, and the welding wire 15. It is comprised from the feeding part 14 to do. The welding torch 16 is attached to, for example, a welding robot, and welding is performed using the welding torch 16 by the welding robot. Alternatively, the welding torch 16 is held by an operator, for example, and welding is performed by the operator using the welding torch 16. The feeding unit 14 can feed the welding wire 15 in a normal feeding direction D101 toward the welding target 18 and a reverse feeding direction D102 moving away from the welding target 18 opposite to the normal feeding direction D101. In the welding power source 19, AC power input from the input power source 1 is rectified by the primary rectifier 2, converted to AC by the switching unit 3, stepped down by the transformer 4, and the secondary rectifier 5 and DCL (inductance). 6 is applied between the welding wire 15 and the welding object 18. A welding arc 17 is generated between the welding wire 15 and the welding object 18 by the applied electric power, and welding is performed. The welding power source 19 includes a welding voltage detection unit 7 that detects a welding voltage V that is a voltage of the welding wire 15, a welding current detection unit 8 that detects a welding current I flowing through the welding wire 15, and a pulse welding period. And a counter unit 9 that counts the elapsed time of the short-circuit welding period or the number of pulses output. Further, based on the number counted by the counter unit 9, a control switching unit 10 for switching the control of welding output, a setting unit 20 for setting welding conditions and the like, and a pulse welding time for controlling current in a pulse welding period A current control unit 12, a current control unit 11 at the time of short-circuit welding for controlling a current in a short-circuit welding period, and a drive unit 13 are provided. The counter unit 9 is the first welding that occurs after the start of welding is instructed by operating a torch switch provided in the welding torch 16 or by executing an operation program of a welding robot. The contact between the wire 15 and the welding object 18 is detected, and the time is counted or the number of pulses output is counted. Further, the setting unit 20 sets the welding current set for performing welding, the set welding voltage set for performing welding, the feeding speed of the welding wire 15, the type of shield gas, and the welding wire 15. This is for setting the material, the diameter of the welding wire 15, the period of pulse welding, the number of waveform outputs, the period of short-circuit welding, the number of waveform outputs, and the like. In addition, each component which comprises the welding power supply part 19 may each be comprised independently as needed, and you may make it comprise combining a some component.

  Next, the operation of the arc welding apparatus 50 will be described. FIG. 1B is a schematic enlarged cross-sectional view showing a welding part of arc welding in the first embodiment.

  In the arc welding apparatus 50, a shield gas is supplied from the gas supply port to shield the arc and the weld from the outside air, and current is supplied between the welding wire 15 and the welding object 18 from the welding power source 19. As a result, a welding arc 17 is generated on the welding wire 15 and the welding object 18, and the tip of the welding wire 15 and a part of the welding object 18 are melted by the heat of the arc 17. The melted welding wire 15 is dropped onto the welding object 18 to form a molten pool 15P together with a part of the welding object 18 melted by the heat of the welding arc 17. Due to the movement of the welding torch 16 in the welding direction D15 relative to the welding object 18, the bead 18A moves relative to the welding object 18 in the welding direction D15 while the molten pool 15P is formed. The welding object 18 is welded while forming.

  The welding conditions for the welding are preset by the setting unit 20, and the feeding speed of the welding wire 15 is also preset by the setting unit 20. The output of the welding power source unit 19 and the rotation of the motor of the feeding unit 14 are controlled so as to satisfy this setting condition. The welding conditions are controlled by controlling the welding power source 19 so that the welding conditions become the set conditions while monitoring the welding power source 19, and the welding current I and the waveform of the welding current I are the basis of this control. Is obtained from the output of the welding current detector 8.

  FIG. 2 shows the welding current I, welding voltage V, and feeding speed WF of the welding wire 15 of the arc welding apparatus 50 according to the first embodiment. In FIG. 2, the vertical axis represents the welding current I, the welding voltage V, and the feeding speed WF, and the horizontal axis represents time. The feeding speed WF can take both positive and negative values. That is, the value of the feeding speed WF is positive when the welding wire 15 that is a welding electrode is fed in the forward feeding direction D101, and the feeding speed WF is fed when the welding wire 15 is fed in the backward feeding direction D102. The value is negative.

  In the pulse welding period Tp, the welding current I flowing through the welding wire 15 forms a plurality of pulses Pp1 to Pp6 that alternately repeat the values Ip1 to Ip6 of the peak current Ip and the values Ib1 to Ib5 of the base current Ib. I is controlled. In the short-circuit welding period Ts, one or more short-circuit periods Tss1 to Tss3 that short-circuit the welding wire 15 and the welding object 18 and one or more that generate the arc 17 between the welding wire 15 and the welding object 18. The welding current I is controlled so as to shift alternately to the arc periods Tsa1 to Tsa2. The pulse welding period Tp and the short-circuit welding period Ts are alternately repeated so that the pulse welding period Tp follows the short-circuit welding period Ts and the short-circuit welding period Ts follows the pulse welding period Tp.

  The pulse welding period Tp is detected by the waveform of the welding current I detected by the welding current detector 8. The pulse welding period Tp can be detected, for example, by detecting that the welding current I has changed from a value larger than a preset threshold Is to a smaller value. Therefore, by comparing the threshold value Is with the welding current I, the pulses Pp1 to Pp6 in the pulse welding period Tp can be detected. The detection method of the pulses Pp1 to Pp6 is not limited to this example, and any method may be used as long as the pulses Pp1 to Pp6 can be detected.

  The short-circuit welding period Ts can be detected, for example, by detecting that the welding voltage V detected by the welding voltage detector 7 has changed from a value greater than a preset threshold value Vs to a smaller value. At this time, in order not to determine that the short-circuit periods Tss1 to Tss3 are very short micro-shorts, a case where a preset time has elapsed while the welding voltage V is continuously higher than the threshold value Vs is determined as one short-circuit. May be. The short circuit detection method is not limited to this example, and any method may be used as long as each short circuit can be detected.

  In the pulse welding period Tp, a value of the feeding speed WF of the welding wire 15 is set in the setting unit 20 in advance so that the average value of the welding current I does not exceed the critical current in combination with the pulse condition of the setting unit 20. The number of pulses or the length of the pulse welding period Tp is also set in the setting unit 20 in advance. On the other hand, in the short-circuit welding period Ts, a value of the welding voltage V that can stably perform short-circuit welding at the feeding speed WF set by the setting unit 20 is set in advance. The number of shorts between the welding wire 15 and the welding object 18 in the short-circuit welding period Ts, that is, the number of short-circuit periods Tss1 to Tss3 or the length of the short-circuit welding period Ts is also set in the setting unit 20 in advance. Therefore, in the arc welding apparatus 50, when pulse welding is performed based on the number or the length of time set by the setting unit 20, the control switching unit 10 switches to short-circuit welding, and the next is also set by the setting unit 20. Further, the current control unit 12 for pulse welding and the current control unit 11 for short circuit welding are switched by the control switching unit 10 so as to perform short-circuit welding based on the above-mentioned number or length of time, and control output from the current control units 11 and 12 Put out. And the drive part 13 which received the control output of the current control parts 11 and 12 gives a control output to the switching part 3 so that the waveform of the welding current I according to the control output can be obtained. As a result, the welding power source unit 19 outputs the welding current I shown in FIG. 2 and applies it to the welding wire 15 and the welding object 18.

  Similarly, in the pulse welding period Tp and the short-circuit welding period Ts, the control switching unit 10 gives a control output to the feeding unit 14 so that the feeding speed WF of the welding wire 15 becomes a preset feeding speed. Thereby, the feeding unit 14 rotationally drives the motor of the feeding unit 14 so that the feeding speed WF of the welding wire 15 becomes a feeding speed corresponding to the pulse welding period Tp and the short-circuit welding period Ts. At this time, in the pulse welding period Tp, the welding wire 15 is fed at an optimum predetermined constant feeding speed WF3 set in advance by the setting unit 20. On the other hand, the control switching unit 10 changes the feeding speed WF of the welding wire 15 in the short-circuit welding period Ts according to a periodic waveform having an amplitude and a period determined in advance by the setting unit 20. The feeding speed WF shown in FIG. 2 changes according to a sine wave as a periodic waveform. The feeding speed WF may be changed according to another periodic waveform such as a trapezoidal wave. The setting unit 20 counts the number of short circuits set in advance, or opens the short circuit at the pulse start time tps when the time set in advance in the setting unit 20 has elapsed, and the control switching unit 10 sets the pulse welding period Tp. The first pulse Pp1 among the plurality of pulses Pp1 to Pp6 is generated. Even after the pulse start time tps, the predetermined speed of the welding wire 15 in the pulse welding period Tp preset by the setting unit 20 is maintained while the feed speed WF is changed according to the periodic waveform in the short-circuit welding period Ts. When the feed speed WF3 changes toward the feed speed WF3 and the feed speed WF reaches a predetermined feed speed WF3 in the pulse welding period Tp, the feed section 14 feeds the welding wire 15 at the predetermined feed speed WF3. Thereafter, when the number of pulses Pp1 to Pp6 set in advance by the setting unit 20 is counted in the pulse welding period Tp or when the time set in advance by the setting unit 20 has elapsed, the current control unit 12 determines the last pulse Pp6. , The welding current I is changed to a current I3 different from the base current Ib values Ib1 to Ib5 in the pulses Pp1 to Pp6. Using the time when the welding current I changes to the current I3 after the last pulse Pp6 is formed as a trigger, the feed speed WF is set to a predetermined value in the pulse welding period Tp at the feed switching time tvs where the welding current I is the current I3. From the feed speed WF3, the welding wire 15 starts to be fed in the forward feed direction D101 and the reverse feed direction D102 according to the periodic waveform described above. In the first embodiment, the current I3 is smaller than the value Ib5 of the base current Ib immediately before the end of the pulse welding period Tp. Thus, in the first embodiment, the current I3 is smaller than at least one of the values Ib1 to Ib5 of the base current Ib. The current I3 may be smaller than the average value of the base current Ib values Ib1 to Ib5, or may be smaller than the base current Ib values Ib1 to Ib5.

  In FIG. 2, the time when the welding current I is changed to the current I3 is used as a trigger for shifting from the pulse welding period Tp to the short-circuit welding period Ts. In the arc welding in the first embodiment, before the end of the pulse welding period Tp, an arbitrary point in time when the welding current I is reduced to a value smaller than the base current Ib in the pulses Pp1 to Pp6 is set as a trigger, that is, a feeding switching point. It may be tvs. By doing in this way, welding is performed while feeding the welding wire 15 at the optimum feed speed WF in each mode at that time while alternately repeating the pulse welding period Tp and the short-circuit welding period Ts under the set conditions. Go go. As shown in FIG. 2, when there is some variation in the short-circuit periods Tss1 to Tss3 and the arc periods Tsa1 and Tsa2, the feeding speed WF is periodically changed after determining the short circuit or determining the arc (opening of the short circuit). In the control in which the welding wire 15 is fed in the forward feed direction D101 and the reverse feed direction D102 according to the waveform, the above-described variation is likely to appear significantly. In the arc welding in the first embodiment, by changing the feed speed WF according to a periodic waveform having a constant period, the short circuit and the arc operation are promoted according to the periodic waveform. Variations in the length of the arc periods Tsa1 and Tsa2 hardly occur.

  Next, the welding current I in Embodiment 1 will be described. The welding current I in the first embodiment is controlled to be a current I3 smaller than the base current Ib of the pulse Pp6 after the last pulse Pp6 when switching from pulse welding to short-circuit welding. Further, in the first short-circuit period Tss1 when switching from pulse welding to short-circuit welding, the welding current I after detecting a short circuit between the welding wire 15 and the welding object 18 is greater than the base current Ib of the pulses Pp1 to Pp6. It is controlled to a small value. Further, the welding current I is sharply reduced at at least one time point when the short-circuit is detected in the short-circuit welding period Ts and when the neck 15A is detected. Switching from the pulse welding period Tp to the short-circuit welding period Ts is performed after the peak current Ip and the base current Ib determined in advance by the setting unit 20 are alternately repeated and the pulses Pp1 to Pp6 are output a predetermined number of times or a predetermined time. The welding current I is changed to a current I3 different from the base current Ib. Specifically, the welding current I is reduced to a current I3 smaller than the base current Ib, and a short circuit at the start of the short circuit period Tss1, which is the start of the short circuit welding period Ts, is waited for. Thereafter, when the welding voltage detection unit 7 detects a short circuit, in order to suppress a micro short circuit in which the short circuit is opened immediately after the short circuit at the short circuit detection time tsp when the short circuit period Tss1 starts, and to suppress the occurrence of spatter during the short circuit. The welding current I is sharply lowered to the current I4 and held at the current I4 for a predetermined period Tsp1. Thereafter, the welding current I is increased to promote the opening of the short circuit. Further, it is more preferable to perform neck control that sharply lowers the welding current I when the welding voltage detector 7 detects the neck 15A (see FIG. 1B) of the welding wire 15 immediately before the short circuit is opened. As a result, the current I when the short circuit is opened can be reduced, and the occurrence of sputtering can be suppressed. After opening the short circuit at the short circuit opening time point tap at which the arc period Tsa1 starts, the current control unit 11 increases the current I to the current I5 so as not to cause a micro short circuit in the arc period Tsa1, and holds it for a predetermined period Tsp2. Thereafter, the welding current I is reduced so as to promote the occurrence of the next short circuit, that is, so that the next short circuit period Tss2 starts. Then, this operation is repeated, and after the short circuit is performed for the number or time set in advance by the setting unit 20, the pulse welding mode is entered simultaneously with the opening of the short circuit, and the pulse welding period Tp is started. The welding current I is controlled so as to form pulses Pp1 to Pp6 that alternately repeat the peak current Ip and the base current Ib. In the arc welding in the first embodiment, the short-circuit welding period Ts shifts to the pulse welding period Tp after the last short-circuit is opened, that is, after the last short-circuit period Tss3. From the short-circuit welding period Ts to the pulse welding period Tp, after the last short-circuit is opened, that is, after the last short-circuit period Tss3, the feeding speed WF of the welding wire 15 is a predetermined predetermined value in the pulse welding period Tp. It is even better to shift after reaching the feeding speed WF3.

  In consumable electrode arc welding in which a pulse welding period and a short-circuit welding period are alternately repeated, in an arc welding method in which a welding wire as a consumable electrode is supplied at a constant rate during a pulse welding period and a short-circuit welding period, Spatter is likely to occur when opened.

  In the arc welding in the first embodiment, after the last pulse Pp6 when shifting from the pulse welding period Tp to the short-circuit welding period Ts, in other words, when moving from the pulse welding period Tp to the short-circuit welding period Ts, 15 is a welding current having a current I3 smaller than the base current Ib in the pulse welding period Tp immediately before the end of the pulse welding period Tp. Control with I. Thereby, the next short circuit can be promoted, it is possible to perform a short circuit in a state in which the growth of the droplets is suppressed, and the generation of spatter during the short circuit can be suppressed. In addition, by holding the welding current I for a predetermined period at a current I3 smaller than the base current Ib, an undershoot at the time of moving from the peak current Ip in the pulse welding period Tp to the initial current in the short circuit period Tss1 in the short circuit welding period Ts. It can be suppressed and stable welding can be realized. In the first short-circuit period Tss1 when switching from the pulse welding period Tp to the short-circuit welding period Ts, control is performed so that the current I after detection of the short-circuit is set to a current I3 smaller than the base current Ib of the pulse welding period Tp. Thereby, the welding wire 15 and the welding target object 18 can be short-circuited reliably, generation | occurrence | production of the micro short circuit which a short circuit opens immediately after a short circuit can be suppressed, and spatter generation | occurrence | production can be suppressed. By sharply lowering the welding current I at least at one of the time when the short circuit is detected and the time when the neck 15A is detected in the short circuit welding period Ts, the current I at the time of short circuit and short circuit opening can be reduced. Accordingly, it is possible to suppress the occurrence of spatter at the time of short-circuiting and opening of the short-circuiting.

  By controlling the welding current I as described above, even if high-heat pulse welding and low-heat short-circuit welding are alternately repeated in a short time, spattering is performed at the time of switching between the welding periods Tp and Ts. Since a phenomenon such as occurrence hardly occurs, a welding method having the advantages of both welding methods can be realized. Further, heat input can be easily controlled by appropriately combining the number or time of the pulses Pp1 to Pp6 and the number or time of the short-circuit periods Tss1 to Tss3. Further, since the welding wire 15 is periodically fed during the short-circuit welding period Ts, stable welding with a constant short-circuit and arc cycle can be realized. Even when switching from the short-circuit welding period Ts to the pulse welding period Tp, and conversely switching from the pulse welding period Tp to the short-circuit welding period Ts, the welding wire 15 is continuously fed to the periodic waveform in the short-circuit welding period Ts. Since the feeding speed WF does not change discontinuously, stable welding can be realized.

  As described above, in the consumable electrode type arc welding using the arc welding apparatus 50 including the welding wire 15 which is a welding electrode, a plurality of pulse welding periods Tp for performing pulse welding and a plurality of short-circuit welding periods for performing short-circuit welding. The process shifts alternately to Ts. In each pulse welding period Tp of the plurality of pulse welding periods Tp, the welding current I flowing through the welding wire 15 is one or more values Ip1 to Ip6 of the peak current Ip and one or more values Ib1 to Ib5 of the base current Ib. And at least one of one or more values Ib1 to Ib5 of the base current Ib at the feed switching time point tvs after forming the plurality of pulses Pp1 to Pp6 and alternately forming the plurality of pulses Pp1 to Pp6. The welding current I is controlled to be smaller (the current I3). In each short-circuit welding period Ts of a plurality of short-circuit welding periods Ts following each pulse welding period Tp, one or more short-circuit periods Tss1 to Tss3 for short-circuiting the welding wire 15 and the welding object 18; The welding current I is controlled so as to alternately shift to one or more arc periods Tsa1 and Tsa2 in which the arc 17 is generated with the welding object 18. The arc welding apparatus 50 is controlled so that the welding wire 15 is fed in a forward feed direction D101 toward the welding object 18 and a reverse feed direction D102 opposite to the forward feed direction D101. Feeding of the welding wire 15, which is alternately repeated in the forward feed direction D101 and the reverse feed direction D102 at a constant cycle, is started at the feed switching time point tvs, and from the feed switching time point tvs to each short-circuit welding period Ts. Then, the arc welding apparatus 50 is controlled so that the welding wire 15 is fed alternately and repeatedly in the forward feed direction D101 and the reverse feed direction D102 in the above cycle.

  The arc welding apparatus 50 may be controlled so that the welding wire 15 is fed at a constant predetermined feed speed WF3 until the feed switching time tvs in the pulse welding period Tp.

  In the short-circuit welding period Ts, a short circuit between the welding object 18 and the welding wire 15 or the neck 15A of the welding wire 15 may be detected. In this case, when the short circuit or the neck 15A is detected, the welding current I may be reduced.

  In the pulse welding period Tp, the welding current I may be controlled so that the welding current I becomes smaller than the average value of one or more values Ib1 to Ib5 of the base current Ib at the feed switching time tvs.

  Further, in the pulse welding period Tp, the welding current I may be controlled so that the welding current I becomes smaller than one or more values Ib1 to Ib6 of the base current Ib at the feed switching time tvs.

  As described above in detail, in arc welding in the first embodiment, in order to control heat input and shape control of the bead 18A, pulse welding and short-circuit welding are alternately repeated at an arbitrary predetermined number of times. We can realize a welding method that combines advantages. Further, by appropriately combining the number of short-circuit weldings and the number of pulse weldings, heat input can be easily controlled. In addition, the shape of the bead 18A can be improved, and posture welding can be easily performed. The

(Embodiment 2)
FIG. 3 shows the welding current I, the welding voltage V, and the feeding speed WF of the welding wire 15 in the second embodiment. The welding current I, welding voltage V, and feed speed WF shown in FIG. 3 are obtained by the arc welding apparatus 50 shown in FIGS. 1A and 1B. 3, the same reference numerals are assigned to the same portions as those in the first embodiment shown in FIG. The arc welding in the second embodiment shown in FIG. 3 differs from the arc welding in the first embodiment shown in FIG. 2 in the following points. When shifting from the short-circuit welding period Ts to the pulse welding period Tp, the welding current I is at the time tps when the feed speed WF of the welding wire 15 reaches the predetermined feed speed WF3 in the forward feed direction D101 in the pulse welding period Tp. The pulse welding period Tp is started by starting to form the first pulse Pp1. After the time point tps, the feeding speed WF is maintained at a predetermined feeding speed WF3. The peak current Ip is generated almost immediately after the time point tps. In the short-circuit welding period Ts, the feeding control of the welding wire 15 and the control of the welding current I are performed in synchronization.

  The reason for shifting from the short-circuit welding period Ts to the pulse welding period Tp when the feeding speed WF of the welding wire 15 reaches the predetermined feeding speed WF3 in the pulse welding period Tp will be described below. As described above, when the welding wire 15 as a welding electrode is fed in the forward feeding direction D101, the value of the feeding speed WF is positive, and when the welding wire 15 is fed in the backward feeding direction D102, the feeding speed is increased. The value of the speed WF is negative. When the welding wire 15 is fed at a low feeding speed WF, the welding wire 15 is fed at a small feeding speed in the forward feeding direction D101 or fed in the reverse feeding direction D102. If the peak current Ip of the pulse Pp1 is generated before the feeding speed WF reaches the predetermined feeding speed WF3, the feeding speed WF of the welding wire 15 is low, and the feeding speed at which the welding wire 15 is fed. Since the peak current Ip of the pulse Pp1 is generated when the current is small or is fed in the reverse feed direction D102, the welding wire 15 burns up, arc breakage occurs, and stable welding cannot be continued. On the contrary, the base current Ib is output without generating the peak current Ip in the pulse Pp1 for a while from the time point tps when the feed speed WF of the welding wire 15 reaches the predetermined feed speed WF3 in the pulse welding period Tp. In this case, since the welding current I is small, the welding wire 15 may be short-circuited to the welding object 18 and stable pulse welding may not be performed.

  Next, control for synchronizing the feeding control of the welding wire 15 and the control of the welding current I in the short-circuit welding period Ts will be described. For example, in FIG. 3, the welding current I is controlled to be the lowest current I1 when the welding wire feeding speed is the maximum feeding speed WF1 in the short-circuit welding period Ts. Then, the feeding current WF is decelerated and the welding current I is increased, and the welding current I is controlled to be the maximum current I2 when the feeding speed WF is the minimum feeding speed WF2. This cycle is repeated periodically. Based on the feeding speed that is an absolute value of the feeding speed WF that can take positive and negative values, the maximum feeding speed WF1 is the maximum feeding speed in the forward feeding direction D101, and the minimum feeding speed WF2 is reversed. This is the maximum feeding speed in the feeding direction D102.

  Next, the reason why the feeding control of the welding wire 15 and the control of the welding current I are performed synchronously in the short-circuit welding period Ts will be described. With the above control, the welding current I becomes the minimum current I1 when the feed speed WF is the maximum feed speed WF1 in the short-circuit welding period Ts, and therefore the welding wire 15 is hard to melt and moves toward the welding object 18. The welding wire 15 heads at a large maximum feed speed WF1, and therefore a short circuit between the welding wire 15 and the welding object 18 is promoted. Since the welding current I becomes the maximum current I2 when the feeding speed WF is the minimum feeding speed WF2, the welding current I becomes the maximum current I2 while the welding wire 15 is being fed in the reverse feeding direction D102. Therefore, since the welding wire 15 is melted and fed in the reverse feeding direction D102, opening of the short circuit is promoted. By controlling the welding current I in synchronization with the feeding speed WF, even if there is a disturbance such as a change in arc length due to a change in the distance between the welding wire 15 and the welding object 18, it is periodic and stable. Welding can be realized. When the short circuit is performed a predetermined number of times, the feeding speed WF of the welding wire 15 is changed from the minimum feeding speed WF2 to a predetermined predetermined feeding speed WF3 in the pulse welding period Tp preset by the setting unit 20. Transition is made according to the periodic waveform described above. And the peak current Ip of pulse welding is output by using the time when the feeding speed WF reaches the predetermined feeding speed WF3 in the pulse welding period Tp as a trigger. That is, when the feed speed WF reaches the predetermined feed speed WF3, the welding current I starts to form the pulse Pp1, thereby starting the pulse welding period Tp. When the pulses Pp1 to Pp6 are output at a predetermined number of times / time by the setting unit 20, the welding current I is reduced from the peak current Ip to the current I3 smaller than the base current Ib in the last pulse Pp6. It is held for a predetermined period Tsp3. Then, using the feed switching time tvs when the welding current I reaches the current I3 as a trigger, the feed speed WF of the welding wire 15 is accelerated from a predetermined constant feed speed WF3 during the pulse welding period Tp, and the forward feed direction D101. And the control which changes according to the periodic waveform which alternately repeats the reverse feed direction D102 are switched at the feed switching time point tvs. In the arc welding shown in FIG. 3, the time when the welding current I reaches the current I3 is set as the trigger, that is, the feeding switching time tvs. In arc welding in the second embodiment, an arbitrary time point when the welding current I is smaller than the base current Ib may be set as the trigger, that is, the feeding switching time point tvs. As described above, in arc welding in the second embodiment, welding is performed according to the periodic waveform both in the switching from the short-circuit welding period Ts to the pulse welding period Tp and in the switching from the pulse welding period Tp to the short-circuit welding period Ts. Since feeding of the wire 15 can be maintained, stable welding can be realized. The current I3 is made smaller than at least one of one or more values (Ib1 to Ib5) of the base current Ib. The current I3 may be smaller than the average value of one or more values (Ib1 to Ib5) of the base current Ib, and may be smaller than one or more values (Ib1 to Ib5) of the base current Ib.

  Further, in the arc welding in the second embodiment, the welding current I may be sharply reduced when the short circuit is detected or when the neck 15A is detected as in the arc welding in the first embodiment. In that case, the welding current I may be a value equal to or less than the minimum current I1. By sharply reducing the welding current I when the short circuit is detected or when the neck 15A is detected, the occurrence of spatter can be further suppressed. In the second embodiment, since the feeding of the welding wire 15 and the welding current I are controlled in synchronism during the short-circuit welding period Ts, periodic and stable welding can be performed even if there is a disturbance due to variations in arc length or the like. realizable.

  As described above, in the short-circuit welding period Ts, the arc welding apparatus 50 is controlled so that the welding wire 15 is fed alternately and repeatedly in the forward feed direction D101 and the reverse feed direction D102 at a constant cycle. In the pulse welding period Tp, the arc welding apparatus 50 is controlled so that the welding wire 15 is fed in the normal feeding direction D101 at a predetermined feeding speed WF3. In the short-circuit welding period Ts, the welding wire 15 is sent after the transition from one arc period Tsa2 of one or more arc periods Tsa1 and Tsa2 to one short-circuit period Tss3 of one or more short-circuit periods Tss1 to Tss3. The arc welding apparatus 50 is controlled such that the welding current I starts to form the first pulse Pp1 among the plurality of pulses Pp1 to Pp6 when the feeding speed WF to be fed reaches a predetermined feeding speed WF3.

  In the short-circuit welding period Ts, the arc welding apparatus 50 may be controlled so that the feeding speed WF repeats the maximum feeding speed WF1 and the minimum feeding speed WF2 at a constant cycle. In this case, the welding current I is set to the minimum current I1 when the feeding speed WF reaches the maximum feeding speed WF1 in the short-circuit welding period Ts. When the feed speed WF reaches the minimum feed speed WF2 in the short-circuit welding period Ts, the welding current I is set to the maximum current I2.

  In the arc welding method in which the pulse welding period and the short-circuit welding period are alternately repeated, when the method disclosed in Patent Document 2 is used during the short-circuit welding period, the welding wire is reversely fed in response to the detection of the short-circuit, thereby causing a short circuit. Can be opened mechanically, the current when the short circuit is opened can be reduced, and the occurrence of spatter can be reduced. However, the forward feed and reverse feed cycles of the feed speed are controlled according to the occurrence of the arc. Therefore, if the short-circuiting time becomes long, the reverse feed amount of the welding wire becomes large, and if the arc time becomes long, the feeding speed of the welding wire in the normal feeding direction becomes large. For this reason, when the arc changes, the average feed speed, the short-circuit cycle, and the number of short-circuits at the feed speed of the welding wire change, so that it becomes difficult to stabilize the welding. In addition, since discontinuity between the welding wire feed control and the welding current control occurs when the pulse welding period and the short-circuit welding period are switched, welding may become unstable and spatter may occur.

  In the consumable electrode type arc welding control in which the pulse welding period Tp and the short-circuit welding period Ts are alternately repeated in the first and second embodiments, the welding wire 15 is fed in the forward feed direction D101 and the reverse feed direction in the short-circuit welding period Ts. Delivered to D102. Thereby, since a short circuit can be opened mechanically and the welding current I when the short circuit is opened can be reduced, the occurrence of spatter during the short circuit welding period Ts can be reduced. Since the welding wire 15 is fed according to the periodic waveform in the short-circuit welding period Ts, there is little variation in the short-circuit and arc cycles, and stable welding can be realized. Furthermore, by controlling the feeding of the welding wire 15 and the welding current I in synchronism, even if there is some disturbance, the short circuit and the short circuit are surely performed, and stable welding can be realized. By alternately repeating short-circuit welding and pulse welding, heat input control and shape control of the bead 18A are performed, thereby generating a weld defect such as poor fusion or a bead having a defective shape such as drooping of the bead 18A in posture welding. Can be suppressed. Both the pulse welding period Tp and the short-circuit welding period Ts can realize welding with less spatter generation. Even when switching between pulse welding and short-circuit welding, there is no discontinuity between the control of the feeding of the welding wire 15 and the control of the welding current I, so that stable welding with low spatter can be realized. Accordingly, it is possible to reduce subsequent processes such as sputter removal.

  The control method of arc welding in the present invention can realize stable welding and is useful for arc welding for welding an object to be welded.

DESCRIPTION OF SYMBOLS 1 Input power supply 2 Primary rectification part 3 Switching part 4 Transformer 5 Secondary rectification part 6 DCL (inductance)
7 Welding voltage detection unit 8 Welding current detection unit 9 Counter unit 10 Control switching unit 11 Current control unit 12 Current control unit 13 Drive unit 14 Feeding unit 15 Welding wire (welding electrode)
15A Neck 16 Welding torch 17 Welding arc 18 Welding object 19 Welding power supply unit 20 Setting unit 50 Arc welding apparatus D101 Forward feed direction D102 Reverse feed direction I1 Maximum current I2 Minimum current Ib Base current Ip Peak current Pp1 to Pp6 Pulse Tp Pulse welding Period Ts Short-circuit welding period Tss1 to Tss3 Short-circuit period Tsa1 to Tsa3 Arc period tvs Feed switching point

(Embodiment 1)
FIG. 1A is a schematic configuration diagram of an arc welding apparatus 50 according to the first embodiment. The arc welding apparatus 50 mainly feeds a welding power source 19 that supplies power between a welding wire 15 that is a welding electrode that is a consumable electrode and a welding object 18, a welding torch 16, and the welding wire 15. It is comprised from the feeding part 14 to do. The welding torch 16 is attached to, for example, a welding robot, and welding is performed using the welding torch 16 by the welding robot. Alternatively, the welding torch 16 is held by an operator, for example, and welding is performed by the operator using the welding torch 16. The feeding unit 14 can feed the welding wire 15 in a normal feeding direction D101 toward the welding target 18 and a reverse feeding direction D102 moving away from the welding target 18 opposite to the normal feeding direction D101. In the welding power source 19, AC power input from the input power source 1 is rectified by the primary rectifier 2, converted to AC by the switching unit 3, stepped down by the transformer 4, and the secondary rectifier 5 and DCL (inductance). 6 is applied between the welding wire 15 and the welding object 18. A welding arc 17 is generated between the welding wire 15 and the welding object 18 by the applied electric power, and welding is performed. The welding power source 19 includes a welding voltage detection unit 7 that detects a welding voltage V that is a voltage of the welding wire 15, a welding current detection unit 8 that detects a welding current I flowing through the welding wire 15, and a pulse welding period. And a counter unit 9 that counts the elapsed time of the short-circuit welding period or the number of pulses output. Further, the welding power source unit 19 includes a control switching unit 10 for switching the control of welding output based on the number counted by the counter unit 9, a setting unit 20 for setting welding conditions and the like, and a current during the pulse welding period. A current control unit 12 during pulse welding to be controlled, a current control unit 11 during short-circuit welding for controlling current during a short-circuit welding period, and a drive unit 13 are provided. The counter unit 9 is the first welding that occurs after the start of welding is instructed by operating a torch switch provided in the welding torch 16 or by executing an operation program of a welding robot. The contact between the wire 15 and the welding object 18 is detected, and the time is counted or the number of pulses output is counted. Further, the setting unit 20 sets the welding current set for performing welding, the set welding voltage set for performing welding, the feeding speed of the welding wire 15, the type of shield gas, and the welding wire 15. This is for setting the material, the diameter of the welding wire 15, the period of pulse welding, the number of waveform outputs, the period of short-circuit welding, the number of waveform outputs, and the like. In addition, each component which comprises the welding power supply part 19 may each be comprised independently as needed, and you may make it comprise combining a some component.

Similarly, in the pulse welding period Tp and the short-circuit welding period Ts, the control switching unit 10 gives a control output to the feeding unit 14 so that the feeding speed WF of the welding wire 15 becomes a preset feeding speed. Thereby, the feeding unit 14 rotationally drives the motor of the feeding unit 14 so that the feeding speed WF of the welding wire 15 becomes a feeding speed corresponding to the pulse welding period Tp and the short-circuit welding period Ts. At this time, in the pulse welding period Tp, the welding wire 15 is fed at an optimum predetermined constant feeding speed WF3 set in advance by the setting unit 20. On the other hand, the control switching unit 10 changes the feeding speed WF of the welding wire 15 in the short-circuit welding period Ts according to a periodic waveform having an amplitude and a period determined in advance by the setting unit 20. The feeding speed WF shown in FIG. 2 changes according to a sine wave as a periodic waveform. The feeding speed WF may be changed according to another periodic waveform such as a trapezoidal wave. The setting unit 20 counts the number of short circuits set in advance, or opens the short circuit at the pulse start time tps when the time set in advance in the setting unit 20 has elapsed, and the control switching unit 10 sets the pulse welding period Tp. The first pulse Pp1 among the plurality of pulses Pp1 to Pp6 is generated. Even after the pulse start time tps, the predetermined speed of the welding wire 15 in the pulse welding period Tp preset by the setting unit 20 is maintained while the feed speed WF is changed according to the periodic waveform in the short-circuit welding period Ts. When the feed speed WF3 changes toward the feed speed WF3 and the feed speed WF reaches a predetermined feed speed WF3 in the pulse welding period Tp, the feed section 14 feeds the welding wire 15 at the predetermined feed speed WF3. Thereafter, when the number of pulses Pp1 to Pp6 set in advance by the setting unit 20 is counted in the pulse welding period Tp or when the time set in advance by the setting unit 20 has elapsed, the current control unit 12 determines the last pulse Pp6. , The welding current I is changed to a current I3 different from the base current Ib values Ib1 to Ib5 in the pulses Pp1 to Pp6. Using the time when the welding current I changes to the current I3 after the last pulse Pp6 is formed as a trigger, the feed speed WF is set to a predetermined value in the pulse welding period Tp at the feed switching time tvs where the welding current I is the current I3. The feeding wire 15 is changed in accordance with the above-described periodic waveform from the feeding speed WF3, and feeding of the welding wire 15 in the forward feeding direction D101 and the backward feeding direction D102 is started. In the first embodiment, the current I3 is smaller than the value Ib5 of the base current Ib immediately before the end of the pulse welding period Tp. Thus, in the first embodiment, the current I3 is smaller than at least one of the values Ib1 to Ib5 of the base current Ib. The current I3 may be smaller than the average value of the base current Ib values Ib1 to Ib5, or may be smaller than the base current Ib values Ib1 to Ib5.

In FIG. 2, the time when the welding current I is changed to the current I3 is used as a trigger for shifting from the pulse welding period Tp to the short-circuit welding period Ts. In the arc welding in the first embodiment, before the end of the pulse welding period Tp, an arbitrary point in time when the welding current I is reduced to a value smaller than the base current Ib in the pulses Pp1 to Pp6 is set as a trigger, that is, a feeding switching point. It may be tvs. By doing in this way, welding is performed while feeding the welding wire 15 at the optimum feed speed WF in each mode at that time while alternately repeating the pulse welding period Tp and the short-circuit welding period Ts under the set conditions. Go go. As shown in FIG. 2, when there is some variation in the short-circuit periods Tss1 to Tss3 and the arc periods Tsa1 and Tsa2, the feeding speed WF is periodically changed after determining the short circuit or determining the arc (opening of the short circuit). In the control in which the welding wire 15 is fed in the forward feed direction D101 and the reverse feed direction D102 by changing according to the waveform, the above-mentioned variation is likely to appear remarkably. In the arc welding in the first embodiment, by changing the feed speed WF according to a periodic waveform having a constant period, the short circuit and the arc operation are promoted according to the periodic waveform. Variations in the length of the arc periods Tsa1 and Tsa2 hardly occur.

Claims (9)

It is a consumable electrode type arc welding control method using an arc welding apparatus equipped with a welding electrode that shifts alternately to a plurality of pulse welding periods for performing pulse welding and a plurality of short circuit welding periods for performing short circuit welding. And
In each pulse welding period of the plurality of pulse welding periods, a plurality of pulses are formed in which the welding current flowing through the welding electrode alternately repeats one or more values of peak current and one or more values of base current. Controlling the welding current to be less than at least one of the one or more values of the base current at a feed switching time after forming the plurality of pulses;
In each short-circuit welding period of the plurality of short-circuit welding periods following the respective pulse welding periods, one or more short-circuit periods for short-circuiting the welding electrode and the welding object; the welding electrode and the welding object; Controlling the welding current to alternately transition into each of one or more arc periods during which arcs are generated; and
Controlling the arc welding apparatus to feed the welding electrode in a forward feed direction toward the welding object and a reverse feed direction opposite to the forward feed direction;
Including
The step of controlling the arc welding apparatus so as to feed the welding electrode includes the feeding switching of feeding the welding electrode, which is alternately repeated in the forward feeding direction and the backward feeding direction at a constant cycle. Starting at the time point, and feeding the welding electrode alternately and repeatedly in the forward feed direction and the reverse feed direction at the constant cycle over the respective short-circuit welding periods from the feed switching time point. A method for controlling arc welding, comprising the step of controlling an arc welding apparatus. The step of controlling the arc welding apparatus to feed the welding electrode is such that the feeding speed for feeding the welding electrode in the respective short-circuit welding periods is the constant feeding speed and the minimum feeding speed. Controlling the arc welding apparatus to repeat at a cycle of
Controlling the welding current in each of the short-circuit welding periods,
Setting the welding current to the minimum current when the feeding speed reaches the maximum feeding speed in each of the short-circuit welding periods;
A step of setting the welding current as a maximum current when the feeding speed reaches the minimum feeding speed in each of the short-circuit welding periods;
The method for controlling arc welding according to claim 1, comprising: The step of controlling the arc welding apparatus to feed the welding electrode includes feeding the welding electrode at a constant predetermined feeding speed until the feeding switching time in each pulse welding period. The method for controlling arc welding according to claim 1, further comprising a step of controlling the arc welding apparatus. Detecting a short circuit between the welding object and the welding electrode or a neck of the welding electrode in each of the short-circuit welding periods;
4. The arc welding according to claim 1, wherein the step of controlling the welding current in each of the short-circuit welding periods includes a step of reducing the welding current when the short-circuit or the neck is detected. 5. Control method. The step of controlling the welding current in each of the pulse welding periods includes the step of controlling the welding current to be smaller than an average value of the one or more values of the base current at the feed switching time in each of the pulse welding periods. The method of controlling arc welding according to any one of claims 1 to 4, comprising the step of controlling the welding current as described above. The step of controlling the welding current in the respective pulse welding period includes the step of controlling the welding current so that the welding current is smaller than the one or more values of the base current at the feed switching time in the respective pulse welding period. The method for controlling arc welding according to any one of claims 1 to 4, comprising a step of controlling a welding current. It is a consumable electrode type arc welding control method using an arc welding apparatus equipped with a welding electrode that shifts alternately to a plurality of pulse welding periods for performing pulse welding and a plurality of short circuit welding periods for performing short circuit welding. And
In each short-circuit welding period of the plurality of short-circuit welding periods, an arc is generated between one or more short-circuit periods for short-circuiting the welding electrode and the welding object, and the welding electrode and the welding object. Controlling the welding current to alternately transition to each of two or more arc periods;
In the respective pulse welding periods of the plurality of pulse welding periods following the respective short-circuit welding periods, the welding current flowing through the welding electrode forms a plurality of pulses that alternately repeat a peak current and a base current. Controlling the current;
Controlling the arc welding apparatus to feed the welding electrode in a forward feed direction toward the welding object and a reverse feed direction opposite to the forward feed direction;
Including
Controlling the arc welding apparatus to deliver the welding electrode comprises:
In each of the short-circuit welding periods, controlling the arc welding apparatus to alternately feed the welding electrodes in the forward feed direction and the reverse feed direction at a constant cycle;
Controlling the arc welding apparatus to feed the welding electrode in the forward feeding direction at a predetermined feeding speed in each of the pulse welding periods;
Including
Controlling the welding current in each of the short-circuit welding periods,
Supplying the welding electrode after transitioning from one arc period of the one or more arc periods to one short circuit period of the one or more short circuit periods in each of the short circuit welding periods Transition to the respective pulse welding period when the speed reaches the predetermined feeding speed,
Controlling the arc welding apparatus such that the welding current begins to form a first pulse of the plurality of pulses during the respective pulse welding period;
A method for controlling arc welding, including: The step of controlling the arc welding apparatus so as to feed the welding electrode is such that the feeding speed repeats the maximum feeding speed and the minimum feeding speed at the predetermined period in each short-circuit welding period. The step of controlling the arc welding apparatus,
Controlling the welding current in each of the short-circuit welding periods,
Setting the welding current to the minimum current when the feeding speed reaches the maximum feeding speed in each of the short-circuit welding periods;
A step of setting the welding current as a maximum current when the feeding speed reaches the minimum feeding speed in each of the short-circuit welding periods;
The control method of the arc welding of Claim 7 containing these. Detecting a short circuit between the welding object and the welding electrode or a neck of the welding electrode in each of the short-circuit welding periods;
9. The arc welding according to claim 6, wherein controlling the welding current in each short-circuit welding period includes reducing the welding current when the short circuit or the neck is detected. Control method.

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